Global biogeography of mating system variation in seed plants

Abstract

Latitudinal gradients in biotic interactions have been suggested as causes of global patterns of biodiversity and phenotypic variation. Plant biologists have long speculated that outcrossing mating systems are more common at low than high latitudes owing to a greater predictability of plant-pollinator interactions in the tropics; however, these ideas have not previously been tested. Here, we present the first global biogeographic analysis of plant mating systems based on 624 published studies from 492 taxa. We found a weak decline in outcrossing rate towards higher latitudes and among some biomes, but no biogeographic patterns in the frequency of self-incompatibility. Incorporating life history and growth form into biogeographic analyses reduced or eliminated the importance of latitude and biome in predicting outcrossing or self-incompatibility. Our results suggest that biogeographic patterns in mating system are more likely a reflection of the frequency of life forms across latitudes rather than the strength of plant-pollinator interactions.

Plants are more likely to be spiny at mid‐elevations in the Qinghai‐Tibetan Plateau, south‐western China

“…We classified each plant species into one of four life-form categories: annual herbs, perennial herbs, shrubs and trees (Moeller et al, 2017). Of the 10,622 species in our study, 860 were annual herbs (7.95%), 6,709 were perennial herbs (62.02%), 2,313 were shrubs (21.38%) and 740 were trees (6.84%).…”

“…Geographical variation in species interactions is central to our understanding of large-scale patterns in species abundance, diversity and functional traits (Abdala-Roberts, Moreira, Rasmann, Parra-Tabla, & Mooney, 2016;Moeller et al, 2017). Traditional theories, such as the latitudinal herbivory defence hypothesis and the elevational herbivory defence hypothesis, are based on the prediction that biological interactions such as herbivory are stronger at lower latitudes and at lower elevations (Dobzhansky, 1950;Pellissier et al, 2012).…”

The best of both worlds? A review of delayed selfing in flowering plants

“…The distribution of published outcrossing rates suggests that mixed mating species are relatively common (Kalisz and Vogler, 2001;Moeller et al, 2017) but we do not know how many are delayed selfers. A comprehensive survey of floral mechanisms, including monographs and historical botanical literature, might yield a rough estimate of the frequency of delayed selfing.…”

Drivers of large‐scale geographical variation in sexual systems of woody plants

“…Plants with different life-history traits vary considerably in their sexual systems (Barrett & Eckert, 1990;Moeller et al, 2017;Snell & Aarssen, 2005), which suggests that plant life-history traits are also likely to influence the ecology and evolution of sexual systems (Vamosi, Otto, & Barrett, 2003). Phylogenetic analyses have revealed the association between dioecy and woody growth habits (i.e., the long-lived, perennial growth form; Chazdon, Careaga, Webb, & Vargas, 2003;Vamosi et al, 2003).…”

“…Studies indicate that tall individuals of dioecious species can even bypass the flow structures induced by plant morphology (e.g., leaves and branches) to ensure further pollen dispersal and increased mating opportunities(Burd & Allen, 1988;Pickup & Barrett, 2012;Thomson, Letten, Tamme, Edwards, & Moles, 2018).Given the well-documented association between plant height and longevity(Marbà et al, 2007;Moles & Leishman, 2008;F I G U R E 2 Comparison between the proportions of species with different sexual systems across different plant heights. In contrast, short-lived species are expected to have a higher frequency of hermaphrodites, which might explain a higher frequency of hermaphrodites in temperate regions compared with sub-tropical and tropical regions(Moeller et al, 2017). (a) Whole study area.…”